In the context of calculating National Income, here's how each of the given transactions would be treated:

(A) Ramesh sold his car for Rs. 5,00,000 which he used for 2 years: This transaction would not be included in National Income because it's the sale of a used asset, not the production of goods or services.

(B) Interest paid on car loan taken by Mohan: This transaction would not be included in National Income because it represents a transfer payment and not income generated from economic activities.

(C) Interest on debentures: This interest would be included in National Income because it represents income earned from financial investments.

(D) Radha purchased goods worth Rs. 1000 to prepare cakes to be sold in an exhibition: The value of goods produced and sold in the exhibition would be included in National Income.

(E) Profit earned by Reliance Industries from their branch in London: This profit would be included in National Income as it represents income earned from economic activities, even if it is earned abroad.

So, the correct answer is (3) (C) and (E) Only.